Maintaining a proper balance of tear film components is essential for the health of the eye. Normal tear film requires proper amounts of lipid, aqueous and mucin components. The meibomian glands located in both the upper and lower eyelids include various sac-like acini are responsible for secretion of lipid components of tear film known as meibum or sebum into the duct of the gland. The meibum then passes into the orifices surrounded by smooth muscle tissue and the muscle of Riolan, which are presumed to aid in the expression of meibum onto the eye surface. It is believed that the meibomian gland orifices open during a normal blinking reflex to release meibum secretions onto the lid margin and then into the inferior tear meniscus. If the lipid secretions are balanced an adequate lipid layer is maintained at the air interface to minimize evaporation and prevent dry eye states. If the lipid secretions are inadequate the lipid layer is not adequate to minimize evaporation with resulting rapid evaporation leading to dry eye states. Blockade of meibum secretions results in accelerated evaporation of the aqueous layer which, in turn, causes symptoms such as dryness, scratching, irritation, burning, tearing, redness, and itchiness. These symptoms are typical of the pathological condition known as dry eye. Dry eye causes may include aging, medication side effects, diseases, and eye structure problems.
Treatment of dry eye typically includes eye drops, punctal occlusions, medications, and/or surgery. Most commonly, a lubricating eye drop is used for dry eye treatment. Several prescription medications are also available for increasing tear production. More recently, occlusions of the meibomian gland are treated using heat and possibly gentle agitation to remove one or more occlusions of the meibomian gland and restore normal tear production. While these treatments are somewhat effective at removing occlusions, none address underlying etiology of dry eye—suboptimal transfer of meibum from the meibomian glands to the eye surface.
Thus, there is a need for new methods for treatment or prevention of dry eye syndrome.